Approximately 400 million cubic yards of sediment are dredged from harbors and waterways in the U.S. each year and up to 12 million cubic yards of very contaminated sediments are handled with special remediation strategies. Heavy metals are one of the most frequently reported contaminants and are problematic with respect to dredge material management. They impact sediment restoration activities throughout the U.S. The lack of available disposal space, the presence of multiple contaminants, and the lack of cost efficient technologies to treat the materials imposes a bottleneck on dredging operations, thus impacting navigation in harbors and waterways. The continued pressing needs for navigable waterways means that innovative dredge material management strategies are needed so that dredging can occur in an environmentally beneficial and cost effective manner.
Disposal sites are used for either the temporary or permanent disposal of contaminated sediments and dredged materials. Until recently, ex situ or terrestrial-based confined disposal systems (landfills) had been widely used for contaminated sediment and dredged materials disposal. However, difficulties in siting landfills as well as the premium placed on the disposal of municipal, industrial, and hazardous wastes in landfills, means that consideration is again being given to coastal, near-shore, off-shore or subsurface disposal in confined disposal sites.
FIG. 1 (from NRC, 1997) depicts some of the types of disposal sites that are currently used for waste containment and disposal. These facilities are designed to meet storage requirements for the contaminated materials and to ensure the control of contaminant release. Each is described below: